Attention has recently been drawn to studies on organic semiconductor structures using an organic semiconductor material, and application of organic semiconductor structures to various devices has been expected. Devices utilizable, for example, in large-area flexible display devices, for example, thin-film transistors (also known as “organic TFTs”), luminescent elements, and solar cells are being studied for such application.
In order to utilize organic semiconductor structures on a practical level, the organic semiconductor layer formed of an organic semiconductor material should exhibit stable charge mobility in a wide service temperature range, and, at the same time, even thin film should be easily formed in a wide area. In particular, properties satisfying the following requirements are desired: the formation of a film by coating rather than film formation by conventional techniques such as vapor deposition is possible; properties in a film formation environment are stable; and stable high charge mobility can be exhibited in a wide service temperature range including room temperature (about −40 to +90° C.).
Regarding prior art documents relevant to the present invention, for example, non-patent documents 1 and 2 describe thiazolothiazole derivatives represented by the following chemical formulae 3 to 5. These documents describe that the thiazolothiazole derivatives represented by the following chemical formulae 4 and 5 can realize transistor operation. In these cases, however, film formation is carried out by vapor deposition, and, further, there is no description on liquid crystallinity and solubility in solvents of the thiazolothiazole derivatives.

Non-patent document 1: S. Ando, J. Nishida, et al., J. Mater. Chem., vol. 14, p. 1787-1790 (2004)
Non-patent document 2: S. Ando, J. Nishida, et al., Chemistry Letters, vol. 33, No 9, p. 1170-1171 (2004)